Proposes a framework for understanding people's theories about their own cognition. Metacognitive theories are defined broadly as systematic frameworks used to explain and direct cognition, metacognitive knowledge, and regulatory skills. The author distinguishes tacit, informal, and formal metacognitive theories and discusses critical differences among them using criteria borrowed from the developmental literature. Sources of metacognitive theories include cultural learning, individual construction, and peer interaction. Implications for educational research and practice are discussed.